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9.7.5 - Corrosion allowances
Gas side: 0 mm
Heat exchange fluid side: 1 mm for tubular plates in lightly
alloyed steels, 0 mm for stainless steel plates or plates with
copper-nickel or stainless steel protection.
9.7.6 - Evaporator
30XAV chillers use a flooded multi-tube evaporator. The water
circulates in the tubes and the refrigerant is on the outside
in the shell. One vessel is used to serve both refrigerant
circuits. There is a centre tube sheet which separates the two
refrigerant circuits. The tubes are 3/4” diameter copper with
an enhanced surface inside and out. There is just one water
circuit with two water passes (one pass when 100C is
selected).
The evaporator has been tested and stamped in accordance
with the applicable pressure code. The maximum maximum
standard relative operating pressure is 2100 kPa for refrigerant
side and 1000 kPa for water side. These pressures can be
different depending on the regulation and the code applied.
The evaporator has a thermal insulation of 19 mm thick
polyurethane foam, aluminium cladding may be fitted as an
option and is equipped with a water vent and purge.
The water connection of the heat exchanger is a Victaulic
connection. As an option the evaporator is available with
freeze protection (evaporator freeze protection option).
The products that may be added for thermal insulation of
the containers during the water piping connection procedure
must be chemically neutral in relation to the materials and
coatings to which they are applied. This is also the case for
the products originally supplied by Carrier.
9.7.7 - Oil separator
In these units, the oil separator is a pressure vessel that is
mounted under the outside vertical condenser coils.
Discharge gas at the compressor outlet is directed towards
the bottom of the oil separator and most of the oil separates
from the gas by strong deceleration and by gravity. The gas
then flows through a wire mesh screen where the remaining
oil is separated by coalescence and flows to the bottom of
the vessel. The gas is now free from oil and leaves the vessel
at the top towards the condenser.
The oil separator is equipped with a trace heater regulated
by the unit controls.
9.7.8 - Assembly function
The assembly function includes a liquid line valve, a filter
drier, two EXVs, a plate heat exchanger as well as protection
devices (seal or valve).
At the condenser outlet a part of the liquid is expanded via
the secondary EXV in one of the heat exchanger port and
then returns as gas at the compressor economiser. This
expansion increases the sub-cooling of the bulk of the liquid
refrigerant which then flows into the evaporator via the main
EXV. This increases both the capacity and efficiency of the
system.
9.8 - High-pressure safety switch
30XAV units are equipped with high-pressure safety switches.
In accordance with the applicable code the high-pressure
switches with manual reset, called PZH (former DBK), may
be backed up by high-pressure switches that require resetting
with a tool. The high-pressure switches that require resetting
with a tool are called PZHH (former SDBK). If a PZHH
cuts out, the corresponding PZH in the same compressor is
faulty and must be replaced. The PZHH must be reset with
a blunt tool with a diameter of less than 6 mm. Insert this
tool into the opening on the pressure switch and push the
reset.
These pressure switches are located at the discharge of each
compressor.
9.9 - Condensers
30XAV coils are all-aluminium micro-channel condensers.
9.10 - Fans
The fans are axial Flying Bird fans equipped with rotating
shroud and made of composite recyclable material. Each
motor is fixed with transverse supports. The motors are
three-phase, with permanently lubricated bearings and
insulation class F (level IP55).
All fans in the same refrigerant circuit are controlled by one
or two variable speed drives. Therefore, they operate together
at the same rotational speed. The rotational speed at full load
or partial load of each circuit is controlled by an algorithm
that continuously optimises the condensing temperature to
obtain the best energy efficiency (EER) whatever the
operating conditions.
9.10.1 - Fan motor electrical protection
The motors of a same circuit are electrically protected by the
variable frequency drive in case of short-circuit, locked rotor
or general overload. Each variable frequency drive follows
a variable current characteristic, based on the frequency from
5 to 50 Hz and the number of fans controlled.
In case of fan failure (in open circuit), the variable frequency
drive will automatically detect the problem and send an alert
to the user interface. Refer to the 30XAV control manual for
the list of alarms specific to this option.
Summary of Contents for AquaForce 30XAV 1050
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